IPT: the killer app

Probably the key application that you can use with a converged network, IP telephony (IPT), probably also needs the most...

Probably the key application that you can use with a converged network, IP telephony (IPT), probably also needs the most investigation. Many people simply think IPT is synonymous with voice over IP; that would be a mistake. Ross Bentley sees what IPT is, and isn't, and shows how you can make it work for you

According to Don Proctor, vice president and general manager at Cisco and a man on the extreme upper lip of the IPT adoption curve, what is described as convergence today differs from what people defined as convergence five years ago. "Then, we talked about media convergence: voice, video and data over the same network, and reaping the advantages of no longer having to maintain multiple networks," he says.

"But today we're entering a new phase: convergence of the user experience. This represents the bringing together all of the disparate communications systems people use - whether it's voicemail, email, instant messaging or video conferencing - into a single, unified communications experience."

What Proctor underlines here is the difference between simple convergence and IP telephony - terms that, together with voice over internet protocol (VoIP), are often used in the same breath, but in reality are distinct from each other.

Discrete packets

Whereas convergence refers to the physical act of running both voice and data traffic over one network, VoIP is the basic mechanism for delivering voice over an IP infrastructure, including the public internet, in digital form in discrete packets rather than in the traditional circuit-committed protocols of the public switched telephone network.

IP telephony, however, takes matters a step forward and allows VoIP calls to retain the features and applications associated with a traditional business telephony system, such as call handling, forwarding, transfer and call back when free. It also allows valuable extra functionality such as directory services, video services and support for multi-channel contact centres. For mobile workers, IP telephony provides further benefits such as speech-enabled access to voice messages and directory services

"IP telephony brings the full richness of PBX to an IP system, then takes it to another level. It is the professional way of building on VoIP," says Andy Clemens, senior marketing manager at BT Business.

While you may already have realised the benefits of convergence, Clemens says the next step is to upgrade to IP telephony. This can be achieved by adding to an existing convergent (or hybrid) switch, or provided by a new IP switch platform. "IP telephony brings even more benefits to a business' converged network and makes deployment more effective," he says.

As its name implies, IP telephony starts with the encoding of voice into IP packets. With IPT it becomes necessary to prioritise the voice packets over other data in order to avoid delays that would seriously detract from speech quality. This is effected by a technique known as Quality of Service (QoS), whereby all packets are classified, and important packets (such as voice) are prioritised above less important packets. So with IPT the LAN needs to be QoS-enabled - which involves, for example, replacing switches with QoS-enabled switches.

IP telephony is also associated with transferring VoIP calls over a secure wide area network (WAN) or virtual private network (VPN) to save on the cost of calls between sites. Again, the WAN or VPN requires QoS, sometimes referred to as Class of Service (CoS). It also requires the network to be properly dimensioned. Having done this, IPT then enables calls between sites to be routed over the company network to avoid traditional telephony costs

Circumnavigating PSTN

For this reason, organisations with multiple sites have most to gain from IP telephony, according to Clemens. Significant cost savings can be achieved by multi-site businesses using their own network for IP telephony calls between sites and avoiding call charges by circumnavigating the PSTN (public switch telephone network).

Connecting satellite offices to the voice network is straightforward compared with traditional telephony systems where every site needed a switch. In the IP telephony world, a switch may only be required at head office, with other sites just needing IP phones.

This plug-and-play approach also makes remote working much easier, enabling devices such as IP phones and soft phones with a pre-configured IP address to be connected to an IP network with pre-existing functionality and profiles. It also allows comprehensive access to corporate functionality, features and security as if staff were simply working in the office.

This flexibility makes network administration cheaper and simpler, too. Your phones can be unplugged and moved at will, and an administrator can easily make changes to movers, leavers and joiners on any PC, without needing a dedicated terminal. This level of simplicity also has benefits in terms of the scalability of your network.

"IP telephony gives businesses a further return on their investment in convergence, and allows them to promote a 'big company feel', both internally and to their customers and suppliers," says Clemens.

Internet telephony benefits  

  • Significant cost savings can be achieved by multi-site businesses using their own network for IP telephony calls between sites, thus avoiding call charges. 
  • Support for remote or smaller sites. Internet telephony can be extended to other sites more cheaply than with traditional systems because the remote sites may require only IP handsets to get up and running.  
  • Better applications. Internet telephony allows your business to adopt call centre and customer management applications much easier. With common standards and open interfaces, implementation is simpler and cheaper.  
  • The overheads of IT and communications management are reduced with internet telephony. From an administrator's perspective, internet telephony allows your entire voice and data network to be viewed from a single management terminal.

Read more on Voice networking and VoIP

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